Blockchain-implemented method and system

ABSTRACT

The invention provides a novel and advantageous solution for controlling or influencing use of and/or access to a resource. This resource may be a device, such as an IoT (Internet of Things) device or a process. The invention is implemented via a distributed ledger (blockchain). This may be the Bitcoin blockchain or some alternative blockchain platform/protocol. In an illustrative embodiment, the controlled resource is a parking meter. The invention may provide a method comprising the steps of generating a blockchain transaction (Tx) indicative of a condition on use of the resource, the blockchain transaction comprising a multi-signature script requiring a plurality of signatures for completion of the blockchain transaction; providing a first subset of the plurality of signatures to the blockchain transaction to generate a partially signed signature script to partially complete the blockchain transaction; and responsive to the condition on the use of the resource being satisfied, providing a second subset of the plurality of signatures to the blockchain transaction to fully complete the blockchain transaction. The condition on the use of the resource may be the use of a discrete amount of the resource and the second subset of the plurality of signatures is provided responsive to the discrete amount of the resource being used.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/320,969, filed Jan. 25, 2019, entitled “BLOCKCHAIN-IMPLEMENTED METHODAND SYSTEM,” which is a 371 Nationalization of International PatentApplication No. PCT/IB2017/054429, filed Jul. 21, 2017, entitled“BLOCKCHAIN-IMPLEMENTED METHOD AND SYSTEM,” which claims priority toUnited Kingdom Patent Application No. 1613144.3, filed Jul. 29, 2016,the disclosures of which are herein incorporated by reference in theirentirety.

The invention relates generally to Distributed Ledger Technologies(DLTs), and more particularly the use of a blockchain for controllingthe use of a resource. Aspects of the invention relate also to theInternet of Things (IoT). The invention may be suited for controlling anIoT device.

In this document we use the term ‘blockchain’ for the sake ofconvenience and ease of reference because it is currently the mostwidely known term in this context. The term is used herein to includeall forms of electronic, computer-based distributed ledgers, includingconsensus-based blockchains, alt-chains, sidechains andtransaction-chain technologies, private and public ledgers, permissionedand un-permissioned ledgers, shared ledgers and variations thereof.

A blockchain is an electronic ledger which is implemented as acomputer-based decentralised, distributed system made up of blocks whichin turn are made up of transactions. Each transaction includes at leastone input and at least one output. Each block contains a hash of theprevious block to that blocks become chained together to create apermanent, unalterable record of all transactions which have beenwritten to the blockchain since its inception. Transactions containsmall programs known as scripts embedded into their inputs and outputs,which specify how and by whom the outputs of the transactions can beaccessed. On the Bitcoin platform, these scripts are written using astack-based scripting language.

In order for a transaction to be written to the blockchain, it must bei) validated by the first node that receives the transaction—if thetransaction is validated, the node relays it to the other nodes in thenetwork; and ii) added to a new block built by a miner; and iii) mined,i.e. added to the public ledger of past transactions.

The most widely known application of blockchain technology is theBitcoin ledger, although other blockchain implementations have beenproposed and developed. While Bitcoin may be referred to herein for thepurpose of convenience and illustration, it should be noted that theinvention is not limited to use with the Bitcoin blockchain andalternative blockchain implementations fall within the scope of theinvention.

Blockchain technology is most widely known for the use of cryptocurrencyimplementation. However, in more recent times, digital entrepreneurshave begun exploring both the use of the cryptographic security systemBitcoin is based on, and the data that can be stored on the Blockchain,to implement new systems.

One area of current interest and research is the use of the blockchainfor the implementation of “smart contracts”. These are computer programsdesigned to automate the execution of the terms of a contract oragreement. Unlike a traditional contract which would be written innatural language, a smart contract is a machine executable program whichcomprises rules that can process inputs in order to produce results,which can then cause actions to be performed dependent upon thoseresults. Another area of blockchain-related interest is the use of‘tokens’ (or ‘coloured coins’) to represent and transfer real-worldentities via the blockchain. A potentially sensitive or secret item canbe represented by the token, which has no discernable meaning or value.The token thus serves as an identifier that allows the real-world itemto be referenced.

The invention also relates to the use of a blockchain-implementedmechanism to control access to a resource. This resource can be aphysical resource such as an “internet of things (IoT)” device. IoT hasbeen described by Wikipedia as “the network of physical devices,vehicles, buildings and other items embedded with electronics, software,sensors, and network connectivity that enables these objects to collectand exchange data . . . The IoT allows objects to be sensed andcontrolled remotely across existing network infrastructure”. In otherembodiments, the resource may be a non-physical resource such as anetwork or software, a portion of cryptocurrency or any other form ofasset.

The present invention is defined in the appended claims.

The present invention provides a computer-implemented method andcorresponding system. The invention may provide a blockchain implementedcontrol method. The method may be arranged to enable, influence, manageor control of use and/or access to a resource. The resource may be aninternet-enabled resource. It may be an IoT (Internet of Things)resource. The resource may be a physical resource such as a device orapparatus, or a process. The resource may be a computer-based resourcesuch as a network or piece of software.

The method may comprise the steps:

generating a blockchain transaction (TxA) indicative of a condition onuse of the resource. The blockchain transaction may comprise amulti-signature script requiring a plurality of (digital) signatures forcompletion of the blockchain transaction; and/or

providing a first subset of the plurality of signatures to theblockchain transaction to generate a partially signed signature scriptto partially complete the blockchain transaction; and/or

responsive to the condition on the use of the resource being satisfied,providing a second subset of the plurality of signatures to theblockchain transaction to fully complete the blockchain transaction(TxA).

By providing such a method, the advantage is provided that use of/accessto the resource can be securely performed and immutably recorded. Forthe sake of readability, we may hereafter simply refer to “use of” theresource, and not repeat the term “and/or access to”.

The condition on the use of the resource may be the use of a discreteamount of the resource and the second subset of the plurality ofsignatures may be provided responsive to the discrete amount of theresource being used. The condition on the use of the resource may bespecified or defined in a smart contract. The smart contract may bestored off the blockchain but referenced from the blockchain eg usingmetadata provided within a transaction.

This provides the advantage that the resource may be used or consumedincrementally.

In the event that the condition on the use of/access to the resource isnot satisfied: access to, or use of, the resource may be prohibited oraltered or restricted; and/or an alert or notification may be sent to adestination.

A plurality of transactions may be generated. These may be partiallysigned transactions. They may be multi-signature transactions. The finalstep of providing the second subset of the plurality of signatures totransaction TxA to complete transaction TxA may comprise: selecting thetransaction (TxA) from the plurality transactions. Each of the pluralityof transactions may be arranged to spend the same output of a previoustransaction (Tx1). (“Previous” meaning that the transaction whichincludes the output precedes the plurality of transactions on theblockchain). Thus, upon determination that the condition has been met,the transaction (TxA) may be selected from the plurality of partiallysigned transactions, and completed. Selection and/or completion of thetransaction may comprise provision of the agent's cryptographic key, andmay be performed by an agent. The agent may be a suitably-programmedautomated resource. The agent may submit the selected transaction (TxA)to the blockchain network. Validation of the transaction on theblockchain may cause an asset such as a portion of cryptocurrency, to betransferred from one party to another by spending a transaction output(TX1 output) on the blockchain.

Each of the transactions in the plurality may be indicative of adifferent condition relating to the use of the resource. Thus, theplurality of transactions may implement a plurality of conditions (orscenarios) relating to the use of the resource. By selecting whichtransaction to complete and submit, the invention controls how theoutput of the transaction (Tx1) is spent and how the cryptocurrencyassociated with the output is transferred.

Satisfaction of the condition(s) may be determined by an agent using aninput or signal to evaluate the condition. This input or signal may begenerated by the agent, or may be received from another source. Theinput or signal may be, for example, detection of a physical orelectronic state, a point in time or any other input.

Generating a blockchain transaction indicative of a condition on use ofthe resource may comprise generating a blockchain transactioncorresponding to each integer multiple of the discrete amount of theresource and the second subset of the plurality of signatures may beprovided for use of each increasing integer multiple of the resource.

This provides the advantage of providing a range of possible useoptions, thereby increasing the versatility of the method. For example,portions or amount of network usage, or length of time that a resourcesuch as a parking space, device etc is used.

A maximum limit on the integer multiple may be pre-defined.

This provides the advantage of allowing consequences due to overuse ofthe resource to be implied and enforced.

Responsive to the exceedance of the maximum limit, an off-block actionmay be generated. The term ‘off-block’ may be construed as meaning ‘notvia the blockchain’.

This provides the advantage of providing consequences due to overuse ofthe resource to be carried out.

The first subset of the plurality of signatures may comprise a signaturefrom an agent. The agent may be a computing-based resource.

This provides the advantage of increasing the security of the method.

The first subset of the plurality of signatures may comprise a signaturefrom an issuer or owner or controller of the resource.

The second subset of the plurality of signatures may comprise asignature from an agent.

The second subset of the plurality of signatures may comprise asignature from a user of the resource.

This provides the advantage of preventing either the issuer or the userfrom exploiting the method.

The condition on use of the resource may be that a zero amount of theresource has been used.

This provides the advantage of defining conditions for a refund to beissued.

The blockchain transaction may have a non-zero locking time.

This provides the advantage of preventing the user from exploiting themethod.

The invention may also provide a system comprising a computer-basedresource arranged or configured to carry out a method according to anyembodiment of the method described herein. Any feature(s) mentioned inrelation to one aspect or embodiment of the invention may also beapplied to any other aspect or embodiment. Any feature(s) mentioned inrelation to the method may be applied to the system of the invention andvice versa. An embodiment of the invention may be arranged substantiallyas described below.

These and other aspects of the present invention will be apparent fromand elucidated with reference to, the embodiment described herein.

An embodiment of the present invention will now be described, by way ofexample only, and with reference to the accompany drawings, in which:

FIG. 1a is a schematic illustration of a system in accordance with theembodiment;

FIG. 1b is flowchart illustrating how a customer may set up a series ofblockchain transactions to pay for parking using the system;

FIG. 2 is a transaction by which Alice pays for her parking for aninitial period;

FIG. 3 is a transaction generated by an agent and sent to Bob for hissignature before signature by the agent when the parking space has beenused for a period of 10 minutes over the time;

FIGS. 4a and 4b schematically illustrate different scenarios in respectof the use of the parking space; and

FIG. 5 is a transaction generated by an agent which is signed by theagent and sent to Alice when the excess time is not used.

OVERVIEW

The invention provides a novel technique for permitting use of and/oraccess to a controlled resource, or managing access to/use of theresource. This is achieved via the use of multiple blockchaintransactions which implement different use/access scenarios relating tothe use or access. For example, a transaction relating to use of theresource for specified period of time, and another relating to use ofthe resource for a different period of time.

The user (ie the person accessing or using the resource) performs adeliberate “double spend” attempt on the blockchain. As known in theart, a “double spend” occurs when a user manages to spend the sameportion of cryptocurrency e.g. Bitcoins twice. Clearly, double spendsare undesirable in the conventional context, as at least one party willbe disadvantaged by not receiving the funds that they were expecting orlegitimately owed. The Bitcoin protocol protects against double spendsvia its verification mechanism. The present invention therefore takes aprocess which is conventionally undesirable and uses it to advantage,for authorization purposes.

In accordance with the present invention, the resource user provides anasset to the resource controller. This asset may be a portion ofcryptocurrency which we will refer to as Bitcoin(s) for the sake ofconvenience, although other cryptocurrencies could be used. The amountof that Bitcoins is determined by a set of condition rules that aretypically defined within a smart contract. The smart contract is ablockchain-implemented, machine executable document and may be storedoff-chain but referenced via a blockchain transaction (Tx). Thecondition rules can include various rules, criteria and parameters etcwhich govern or define the authorised, legitimate use/access of theresource. In a preferred embodiment, these condition rules are evaluatedby an independent party i.e. a party other than the resource user orcontroller.

Thus, advantageously, the resource controller has certainty that theconditions will be fulfilled, without having to know the details of thefulfilment conditions as these will be determined and enforced by anindependent party. This may be an automated agent, which may be referredto as an oracle. The oracle determines fulfilment of the conditionsbased on an evaluation that is performed. This could be whenuse/release/access to the resource is permitted, or at a pre-determinedtime, or when a trigger event is detected etc. This assessment enablesthe oracle to select one of the proposed blockchain transactions forprogression to completion. This is achieved by providing the oracle'scryptographic signature to the selected transaction. Thus, there is anexternal oracle, evaluating the condition(s) provided by the smartcontract and based upon parameters relating to use/access e.g. how longthe resource has been used for, determining which of the plurality ofpresented transactions (Txs) is completed. This then automaticallyinvalidates the other proposed transaction(s).

Responsive steps can be taken by the oracle and/or resource controllerin the event that the oracle or agent determines that the condition(s)are not met. For example, use/access to the resource can be denied, alocking mechanism can be applied or configured, or a communication suchas an alert may sent to a recipient, and/or a refund transaction may besubmitted to the blockchain network.

Illustrative Use Case

We describe a system in accordance with an illustrative embodiment usingthe example of a car parking space where a fee is charged for parking inthe space. Participating car parking space owners (either establishedparking space operators or small businesses or private individuals withavailable and desirable parking spaces) attach an IOT device 104 to theparking spot. The invention is not limited, however, to use with parkingmeters. Other types of controlled, internet-enabled resources may be thesubject of the invention instead.

The IOT device 104 is capable of detecting the presence of a parkedvehicle (as is already common practice). The device may be a part of, ormay be, a Blockchain IOT Device 106. A programmable “Blockchain IOTDevice (BID)” is an internet-enabled device which is also able tomonitor, interact with and publish to a blockchain network.

Vehicle drivers download a smartphone app (or a ‘smart car’ app—i.e. anapp designed to run on car computers) compatible with the carpark BID106. The app allows the driver to pay for the car space via theBlockchain using cryptocurrency or tokenised cryptocurrency.

The parking service may be represented using a smart contract. This is amachine readable and executable document. The terms and conditions inthe contract are referenced using metadata in Transactions (Txs) thatpoint to the location of the contract file on a DHT. In otherembodiments, the contract could be stored in any other form of databaseor storage arrangement. The terms and conditions set out in the contractmay include the following:

-   -   The vehicle ID (e.g. number plate)    -   The start-time for parking    -   The expiry time    -   The car space identifier (e.g. Precise GPS location, or        residential address, or address+a sequential number (which may        also be painted on the actual space or otherwise indicated at        the physical location of the space)    -   The rate (which may be expressed for example in satoshis/minute,        or $/minute, etc)    -   Other complex conditions such as:        -   First 2 hours (or other period) free        -   Cost is in partial periods (e.g. ‘0.01BTC per hour or part            thereof’)

In some embodiments the BID 106 is able to identify the vehicle via oneof several methods, for example the BID 106 may include an inbuiltcamera aimed at the general area of vehicle number plates; in anotherexample the BID 106 detects a unique signal ID emitted by the vehicle,in another example a purpose built car-tag RFID is attached to thevehicle. In some embodiments the BID 106 is not able to identify thevehicle (e.g. for privacy purposes) and instead parking attendants areable to verify the correct vehicle is parked by visually checking thenumber plate against the number plate registered in the payingTransaction.

The app may allow a range of functions, for example:

-   -   The driver can reserve the spot for a future period        -   The reservation may require a pre-payment in bitcoin (or            not)    -   The driver can set the app to automatically pay for and roll        over for another period (adjustable) if the paid time expires.    -   The app may allow for regular parking (e.g. reserved for        weekdays)

As illustrated in FIG. 1a , System 100 comprises the car parking space102, the Internet-enabled (Internet-of-Things or “IoT”) device 104, theBlockchain Internet-of-Things device (BID) 106, a blockchain server 108which is operative to provide access to the peer-to-peer network whichunderpins the blockchain, and an agent 110 which is operative to monitorthe blockchain and is in communication with the IoT device 104 and theBID 106.

We now describe the use of a parking space using system 100 withreference to the flowchart in FIG. 1b . Alice has a smartphone app thatindicates the location of available car spaces by interrogating theBlockchain. She locates a convenient spot and parks her car in stepS100. The app indicates the terms and conditions for this space whichcould, for example, be in the driveway of a residence in a denseinner-city location such as London or Los Angeles.

In step S102, Alice accepts the terms and conditions and, afterselecting certain options, uses the app to pay for the space for therequired time in bitcoins. She is not 100% sure she will be back in timeso she also selects the option provided by the application toautomatically pay to extend the parking period by 10 minutes each timeit expires, up to 3 times (she thinks the premium for this facility is abit expensive but she is willing to pay this to avoid the fine andreputation damage if she gets back after expiry).

Of course, Alice knows the smartphone app provides the functionality tosimply extend the period remotely if the expiry time looms, but as shewill be in meetings she cannot be sure she will get that opportunity).Later, Alice returns ahead of the expiry time. Although the smartphoneapp allows her to cancel the unneeded rollovers she knows in this caseshe does not need to because this BID 106 operator has settings thatallow her to simply depart and the BID 106 detects that she has not usedthe rollovers and so (as per contract) automatically cancels therollovers for her.

So, let us assume that Alice rents the parking space for 1 hour at thecost of 5BTC, and the extra time cost is 1BTC/10 minutes.

The first transaction crediting Bob 5BTC is a P2PKH which pays for thefirst hour. This is a standard Bitcoin transaction.

We define T_(extra) as the time Alice's car stays parked on the parkingspace after the nominal time period, i.e. after the first hour which hasalready been paid for.

T_(extra) is a multiple of 10 and takes the values 0, 10, 20, 30. Attime T=60, 70, 80 and 90 minutes, the BID 106 checks if the vehicle isstill parked on the parking space. If not, the BID 106 sends messages toAlice, Bob, the parking space owner, and a third party or “agent”. Themessages include the value T_(extra). For example, if Alice returns tothe parking space at time 65, T_(extra)=10, and Bob should charge Alice1BTC. However, Alice doesn't trust Bob, and she would prefer to use anindependent service to release the funds, and the release should beconditional on the signature of an agent server. The agent acceptsrequests, for example is T_(extra)=10?, evaluates them, and produce anoutput. The agent receives the information from the IoT device 104.

Alice and Bob agree on the rule script and send it to the agent server(O₁). The script might look like this:

If (T_(extra)==10)

-   -   return Sign TxA        else if (T_(extra)==20)    -   return Sign TxB        else if (T_(extra)==30)    -   return Sign TxC        else    -   return False

If O₁ resolves the script favourably, i.e. one of the conditions on theuse of the parking space is satisfied it signs and broadcasts eitherTxA, TxB, or TxC (but not all of them).

The agent generates a new public key in a step S104. The agent obtainspublic keys from Alice and Bob in a step S106. The agent then generatesa 2-of-3 multi-signature address in step S108.

Alice generates a new transaction Tx1 that sends 3BTC to the multisigaddress, signs Tx1 and broadcasts it across the Bitcoin network in astep S110. This transaction is illustrated in FIG. 2.

The agent verifies Tx1 and generates three transactions spending theUTXO of TX1 in a step S112. The three transactions can be denoted asTxA, TxB and TxC. The agent also generates a fourth transaction TxR instep S112. TxA is illustrated in FIG. 3. TxB and TxC are similar but fordiffering amounts of bitcoin as set out below.

As can be seen from FIG. 3, TxA sends 1BTC to Bob and 2BTC to Alice, andcorresponds to T_(extra)=10. TxB sends 2BTC to Bob and 1BTC to Alice,and corresponds to T_(extra)=20. TxC sends 3BTC to Bob, and correspondsto T_(extra)=30.

Each of TxA, TxB and TxC require 2 signatures in the form of Bob'ssignature and the agent's signature. The agent transmits TxA, TxB andTxC to Bob in a step S114. Bob then signs each of TxA, TxB and TxC andreturns them to the agent as incomplete blockchain transactions in astep S116.

TxR is a refund transaction that sends 3BTC back to Alice; it has anon-zero lock time corresponding to a certain moment in the future. TxRrequires two signatures in the form of Alice's signature and the agentsignature. That is to say, if Alice does not use the parking space foran amount of time over what has been paid for in Tx1, a refund willautomatically be issued. TxR is signed by the agent upon generation instep S112. TxR is illustrated in FIG. 5.

Now we consider the example where Alice has parked in the parking spacefor up to 10 minutes over the hour she paid for with Tx1. That is tosay, T_(extra)=10. This is illustrated with reference to FIG. 4 a.

In a step S200, the IOT device 104 detects that Alice's car has beenparked in the space for 10 minutes in excess of the hour paid for inTx1. The BID 106 then communicates that the car has been parked in thespace for the extra 10 minutes to the agent in a step S202, i.e.T_(extra)=10. That is to say, one of the conditions in the script abovehas been evaluated by the agent to true.

The agent then signs TxA to complete the transaction in a step S204. TxAcan then be broadcast to the blockchain in a step S206. The completionof TxA pays 1BTC to Bob and 2BTC to Alice. TxB and TxC can be completedsimilarly.

Now we consider the example where Alice leaves the parking space on timeand T_(extra)=0. This is described with reference to FIG. 4b . In a stepS300, the IoT device 104 detects that Alice has moved her car from theparking space before any excess time has accrued. In step S302, the IoTdevice 104 communicates to the agent that Alice has left the space ontime. In step S304, the IoT device 104 sends TxR to Alice who signs itto complete transaction TxR. The completion of the transaction TxR meansthat Alice has the 3 BTC back. TxR has a non-zero locking time whichmeans that it may not be mined and added to the blockchain until thatlocking time has expired. This means that, provided Alice provides thesignature, TxR is broadcast at some point in the future and notimmediately.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe capable of designing many alternative embodiments without departingfrom the scope of the invention as defined by the appended claims. Inthe claims, any reference signs placed in parentheses shall not beconstrued as limiting the claims. The word “comprising” and “comprises”,and the like, does not exclude the presence of elements or steps otherthan those listed in any claim or the specification as a whole. In thepresent specification, “comprises” means “includes or consists of” and“comprising” means “including or consisting of”. The singular referenceof an element does not exclude the plural reference of such elements andvice-versa. The invention may be implemented by means of hardwarecomprising several distinct elements, and by means of a suitablyprogrammed computer. In a device claim enumerating several means,several of these means may be embodied by one and the same item ofhardware. The mere fact that certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage.

1-14. (canceled)
 15. A blockchain-implemented method of controlling useof and/or access to a resource, the method comprising: generating ablockchain transaction (TxA) indicative of a condition on use of, oraccess to, the resource for a specified period of time, the blockchaintransaction comprising a multi-signature script requiring a plurality ofsignatures for completion of the blockchain transaction; providing afirst subset of the plurality of signatures to the blockchaintransaction (TxA) to generate a partially signed signature script topartially complete the blockchain transaction (S114); and responsive tothe condition on the use of, or access to, the resource being satisfied,providing a second subset of the plurality of signatures (S204) to theblockchain transaction to fully complete the blockchain transaction. 16.The blockchain-implemented method of claim 15, wherein the specifiedperiod of time is defined within a smart contract stored off theblockchain but referenced from the blockchain.
 17. Theblockchain-implemented method of claim 15, wherein the step of providingthe second subset of the plurality of signatures to the blockchaintransaction (TxA) further comprises: selecting the transaction (TxA)from a plurality of partially signed, multi-signature transactions(S112).
 18. The blockchain-implemented method of claim 15, wherein thecondition on the use of the resource is the use of a discrete amount ofthe resource and the second subset of the plurality of signatures isprovided responsive to the discrete amount of the resource being used.19. The blockchain-implemented method of claim 18, wherein generating ablockchain transaction indicative of a condition on use of/access to theresource comprises generating a blockchain transaction corresponding toeach integer multiple of the discrete amount of the resource and thesecond subset of the plurality of signatures is provided for use of eachincreasing integer multiple of the resource.
 20. Theblockchain-implemented method of claim 19, wherein a maximum limit onthe integer multiple is pre-defined.
 21. The blockchain-implementedmethod of claim 20, wherein, responsive to exceedance of the maximumlimit, an off-block action is generated.
 22. The blockchain-implementedmethod of claim 15, wherein the first subset of the plurality ofsignatures comprises a signature from an agent.
 23. Theblockchain-implemented method of claim 15, wherein the first subset ofthe plurality of signatures comprises a signature from an issuer of theresource.
 24. The blockchain-implemented method of claim 23, wherein thesecond subset of the plurality of signatures comprises a signature froman agent.
 25. The blockchain-implemented method of claim 22, wherein thesecond subset of the plurality of signatures comprises a signature froma user of the resource.
 26. The blockchain-implemented method of claim15, wherein the condition on use of the resource is that a zero amountof the resource has been used.
 27. The blockchain-implemented method ofclaim 15, wherein the blockchain transaction has a non-zero lockingtime.
 28. The blockchain-implemented method of claim 15, furthercomprising: submitting the fully completed transaction to the blockchainto spend an output associated with a previous transaction (Tx1).
 29. Asystem comprising a processor and storing memory, the memory includinginstructions that, when executed by the processor, cause the processorto perform the blockchain-implemented method of claim 15.